Make UMA_HISTOGRAM_ENUMERATION work with scoped enums.

ui/events/blink/input_handler_proxy.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/events/blink/input_handler_proxy.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 
@@ skipping 538 matching lines @@
 
   if (device != blink::WebGestureDeviceTouchpad &&
       device != blink::WebGestureDeviceTouchscreen) {
     return;
   }
 
   // UMA_HISTOGRAM_ENUMERATION requires that the enum_max must be strictly
   // greater than the sample value. kMainThreadScrollingReasonCount doesn't
   // include the NotScrollingOnMain enum but the histograms do so adding
   // the +1 is necessary.
-  uint32_t mainThreadScrollingReasonEnumMax =
+  // TODO(dcheng): Fix https://crbug.com/705169 so this isn't needed.
+  constexpr uint32_t kMainThreadScrollingReasonEnumMax =
       cc::MainThreadScrollingReason::kMainThreadScrollingReasonCount + 1;
   if (reasons == cc::MainThreadScrollingReason::kNotScrollingOnMain) {
     if (device == blink::WebGestureDeviceTouchscreen) {
       UMA_HISTOGRAM_ENUMERATION(
           kGestureHistogramName,
           cc::MainThreadScrollingReason::kNotScrollingOnMain,
-          mainThreadScrollingReasonEnumMax);
+          kMainThreadScrollingReasonEnumMax);
     } else {
       UMA_HISTOGRAM_ENUMERATION(
           kWheelHistogramName,
           cc::MainThreadScrollingReason::kNotScrollingOnMain,
-          mainThreadScrollingReasonEnumMax);
+          kMainThreadScrollingReasonEnumMax);
     }
   }
 
   for (uint32_t i = 0;
        i < cc::MainThreadScrollingReason::kMainThreadScrollingReasonCount;
        ++i) {
     unsigned val = 1 << i;
     if (reasons & val) {
       if (val == cc::MainThreadScrollingReason::kHandlingScrollFromMainThread) {
         // We only want to record "Handling scroll from main thread" reason if
         // it's the only reason. If it's not the only reason, the "real" reason
         // for scrolling on main is something else, and we only want to pay
         // attention to that reason.
         if (reasons & ~val)
           continue;
       }
       if (device == blink::WebGestureDeviceTouchscreen) {
         UMA_HISTOGRAM_ENUMERATION(kGestureHistogramName, i + 1,
-                                  mainThreadScrollingReasonEnumMax);
+                                  kMainThreadScrollingReasonEnumMax);
       } else {
         UMA_HISTOGRAM_ENUMERATION(kWheelHistogramName, i + 1,
-                                  mainThreadScrollingReasonEnumMax);
+                                  kMainThreadScrollingReasonEnumMax);
       }
     }
   }
 }
 
 void InputHandlerProxy::RecordScrollingThreadStatus(
     blink::WebGestureDevice device,
     uint32_t reasons) {
   DCHECK(device == blink::WebGestureDeviceTouchpad ||
          device == blink::WebGestureDeviceTouchscreen);
@@ skipping 1012 matching lines @@
                  scroll_elasticity_controller_->GetWeakPtr(), gesture_event,
                  scroll_result));
 }
 
 void InputHandlerProxy::SetTickClockForTesting(
     std::unique_ptr<base::TickClock> tick_clock) {
   tick_clock_ = std::move(tick_clock);
 }
 
 }  // namespace ui